To protect the blade edges of steam turbine blades mainly from erosive attack, these must be provided with a special edge protection. In the case of turbine blades made of chromium steels, this edge protection is achieved by, e.g., inductive hardening, which is technically sufficient in most cases.
According to EP 0,282,831 B1, the edge protection consists, in the case of turbine blades made of titanium alloys, of a heterogeneous powder mixture containing ca. 1/3 part by weight of titanium carbide, titanium nitride or titanium boride, as well as non-oxidizable, martensitic or austenitic-martensitic steel, which mixture is melted by a laser beam, and which is separated from the base material by a sublayer consisting of pure vanadium powder, which is also melted by a laser beam and has a thickness of at least 1 mm.
EP 0,247,582 B1 discloses a process for applying a protective layer to a turbine blade made of a vanadium-containing titanium alloy, according to which a vanadium powder, used as an intermediate layer, is first heated and melted inductively by means of a mobile inductor, and a layer consisting of a cobalt-chromium-tungsten alloy, which is also premelted inductively from a powder, is applied to it.
EP 0,249,092 B1 discloses the soldering of a sintered and mechanically compacted protective cap consisting of a titanium carbide-containing iron-base alloy with high chromium and cobalt contents by means of a thin sheet with a thickness of 70-150 mm based on copper under vacuum or an inert gas at 900.degree.-950.degree. C.
Finally, FR 2,663,343 B1 discloses the preparation of a composite according to the powder metallurgical technology, welding or other methods, such as sintering or hot isostatic pressing. This composite is likewise applied for protecting the turbine blade edge according to temperature-supported processes, e.g., soldering.
Disadvantages, such as intense local heating to above the melting point, mixing, structural changes, internal stresses, relatively coarse weld structures tending to undergo segregation, reduction in the dynamic characteristics of the component, and sometimes the unintended formation of local cells, arise from a metallurgical viewpoint and from the viewpoint of component engineering.